Polymeric lactones containing thioether atoms



United States Patent 3,227,692 PGLYMERIC LACTONES CONTAINING THIOETHER ATBMS James L. Graham, Rochester, N.Y., and John Sagal, In,

Mount Prospect, Ill., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N0 Drawing. Original application Dec. 12, 1958, Ser. No. 779,839, now Patent No. 3,046,129, dated July 24 1962. Divided and this application June 25, 1962, Ser. No. 205,066

6 Claims. ((11. 260-783) This invention relates to polymeric lactones and methods for preparing them. The polymeric lactones of our invention are particularly useful in sensitizing photographic silver halide emulsions, particularly those containing color-forming compounds or couplers.

This application is a division of our application Serial No. 779,839, filed December 12, 1958, now US. Patent No. 3,046,129.

A number of methods have been previously described for increasing the sensitivity of photographic silver halide emulsions, other than methods of optical or spectral sensitization, which involve the incorporation of certain colored compounds or dyes in the emulsions. The incorporation of such dyes in the emulsions increases the optical range of sensitivity, and for this reason such dyes are commonly referred to as optical or spectral sensitizing dyes. It is also Well known to increase the sensitivity of photographic emulsions by addition of sulfur compounds capable of reacting with silver salts to form silver sulfide, or with reducing agents (compounds of these types are also naturally present in gelatin), or with salts of gold or other noble metals, or with combinations of two or more of the aforementioned compounds generally known as chemical sensitizers. Such chemical sensitizers are believed to react with the silver halide to form, on the surface of the silver halide, minute amounts of silver sulfide or of silver or of other noble metals, and these processes are capable of increasing the sensitivity of developing-out emulsions by very large factors. The process of chemical sensitization, however, reaches a definite limit beyond which further addition of sensitizer, or of further digestion with the sensitizer present, merely increases the fog of the photographic emulsion with constant or decreasing speed.

We have now found a means of further increasing the sensitivity of photographic emulsions, which may be applied even though the ordinary processes of chemical sensitization have been carried to the effective limit of the photographic emulsion in question. Our process is to be distinguished from hypersensitization, which is produced by bathing a finished coating with water or with solutions of ammonia, amines or silver salts. Such processes act primarily on optically sensitized photographic emulsions and tend to increase the free silver ion concentration of the emulsion and greatly diminish its stability. Our process is also to be distinguished from hypersensitization by mercury vapor, which gives a transitory effect which is lost on storage of the film. The compounds used in our invention do not appear to be chemical sensitizers in the usual sense, since they increase speed by their presence during exposure and processing and require no digestion with the photographic emulsion to produce the increase in speed, nor does their chemistry indicate that they are likely to react With silver halide under normal emulsion conditions.

The novel sensitizers of our invention are quite unique in that the effects produced are additive in photographic emulsions which have already been sensitized to their optimum, or near-optimum, with conventional chemical sensitizers, such as labile sulfur compounds. The novel "ice sensitizers of our invention, however, can be used to sensitize photographic silver halide emulsions containing no other sensitizers, if desired. The novel sensitizers of our invention are not strictly chemical sensitizers, since chemical sensitizers do not generally provide the additive effects of the type mentioned.

It is, therefore, an object of our invention to provide novel sensitizers for photographic silver halide emulsions, particularly those containing color-forming compounds or couplers. Another object is to provide a novel class of polymeric lactone compounds. Still another object is to provide methods for making these polymeric lactone com.- pounds. Other objects will become apparent from a consideration of the following description and examples.

The polymeric lactone compounds of our invention can be illustrated by the following general formula:

wherein R and R each represents a hydrocarbon alkylene radical, such as methylene, ethylene, trimethylene, butylene, pentamethylene, octamethylene, decamethylene, dodecamethylene, tetradecamethylene, etc., and n represents a positive integer of at least 2. Especially useful polymers represented by the above general formula comprise those wherein n is at least 3, the polymeric lactone therefor, having a molecular weight from about 250 to 10,000, although polymeric materials having a molecular weight from about 500 to 3,500 have been found to be particularly useful in our invention.

The compounds of Formula I can alternatively be written in the following fashion:

wherein R R and n each have the values given above. The linear polymers represented by Formula I above can advantageously be prepared by self-condensation of at least one hydroxy acid (or alternatively, a lactone of the acid) represented by the following general formula:

wherein R and R have the values given above. Acid catalyzed condensation of the compounds of Formula III occurs spontaneously on standing (for several weeks), although it has been found that polymers of Formula III can be prepared more rapidly by heating the lactone of the acid in Formula III in the presence of an acidic condensation agent, such as zinc chloride, p-toluene sulfonic acid, etc.

The following examples will describe the methods of preparing these novel polymers.

EXAMPLE 1 Polymerization of hydroxyethylmercaptoacetic lactone at 180 C. with zinc chloride In glass apparatus, under an air condenser, were placed 10 g. of hydroxyethylmercaptoacetic acid lactone and 0.100 g. of anhydrous zinc chloride. The reaction mixture was heated in an oil bath at 180 C. for 115 minutes. The viscous polymer was cooled and dissolved in ml. of acetone, boiled with decolorizing carbon (Norite) and cooled to room temperature. About five volumes of ether were added and the emulsion obtained was chilled in a Dry Ice-acetone bath. A solid polymer deposited. The ether was poured off cold and the residue was extracted at room temperature with several changes of ether. After the last extraction, the residual ether was removed at room temperature under vacuum and the remaining oil was dissolved in acetone to make g. of solution. The solids content was 2.6 percent. Molecular weight by end-group titration was 7100.

EXAMPLE 2 Polymerization of hydroryetllylmercaploacetic acid lactone by chloracetic acid Twenty-seven grams of lactone were heated in an oil bath at 180 C. with 0.270 g. of chloracetic acid in an allglass reflux outfit for 20% hours. After cooling a viscous, clear, tan dope was obtained. This was thoroughly extracted by kneading with ether. The residual ether in the polymer was removed under vacuum at room temperature. The remaining polymer was then extracted with acetone at room temperature. The acetone filtrates were combined and chilled in a Dry Ice-acetone bath. With chiling, polymer deposited. The cold acetone supernatant was poured off and the remaining polymer was worked with ether until it became friable. It was then dried in a vacuum desiccator under a constantly applied waterpump vacuum. The yield was 3.6 g. molecular weight by end-group titration was 5000.

EXAMPLE 3 1 Polymerization of hydroxyethylmercaptoacetic acid lactone by toluene sulfonic acid EXAMPLE 4 Preparation and polymerization of hydroxypropylmercaplopropionic acid lactone (1) Preparation.In an all-glass reflux outfit were placed 12.5 g. of mercaptopropanol, 9.8 g. of acrylic acid and 0.136 g. of hydroquinone. The reaction mixture Was heated over-night on a steam bath. Volatiles were then removed under vacuum up to a boiling point of 50-53 C. at 0.8 mm. The yield of crude product was 12.4 g,

(2) Polymerization-Six grams of the above reaction product were heated on a steam bath with 0.120 g. of anhydrous zinc chloride under an air-reflux condenser with a slow stream of nitrogen passing through the reaction mixture. After 44 /2 hours, a viscous dope was obtained. After cooling, this was extracted repeatedly with 40 ml. portions of ether, pouring off the supernatant liquid. This removed the unreacted monomer. The residual ether was removed under vacuum at room temperature and the polymer was repeatedly extracted with water to remove hydroquinone. Residual Water was removed under vacuum. A viscous oil remained. In a few days at room temperature, this oil changed to a waxy solid. This was dissolved with warming in 35 ml. of acetone and the solution was chilled in a Dry Ice-acetone bath. White solid polymer deposited. This was filtered onto a chilled Buchner funnel, washed on the funnel with cold acetone, and dried in a vacuum desiccator under a constantly applied water pump vacuum. The yield was 3.2 grams. Elemental analyses were as follows.

Found: C, 48.6; H, 6.85; 5, 21.95. Calculated exclusive of end-groups: C, 49.3; H, 6.9; S, 21.9.

EXAMPLE 5 Polymerization of fi-lzydroxyethylmercaptopropionic acid lactone This polymer was prepared in exactly the manner shown in Example 4 above, using zinc chloride as a catalyst and 4 heating the reaction mixture at 100 C. A white solid polymer was obtained.

EXAMPLE 6 Hydroxyhexylmercaptopropionic acid lactone Mercaptohexanol and acrylic acid were reacted in a manner very similar to the above. Attempts to polymer ize with zinc chloride yielded insoluble products. A soluble product was achieved in the following way:

The lactone (about 25 g.) was heated at 150 C. in a flask immersed in an oil bath under -a high vac pump vacuum of 0.07 mm. The viscosity of the melt rose. After 3 hours, the reaction mixture was cooled. There was practically no flow at room temperature. The polymer was disclosed in 50 ml. of acetone. The solution was diluted with 400 ml. of absolute alcohol and the white suspension chilled in a carbon dioxide snow-acetone bath. Gummy polymer deposited. The supernatant liquid was poured off and the residue extracted repeatedly with fresh portions of absolute alcohol. The residual alcohol was then removed under vacuum with gentle warming. The polymer was then dissolved in 30 ml. of acetone and filtered. Thirty-eight and one-half grams of solution with a solids content of 21.2% were obtained.

EXAMPLE 7 Preparation of the polymer from 'y-hydroxypropylmercaptoacetic acid The preparation of 'y-lzydroxyprapylmercaptoacetic acid lactone.Eighty-three and two-tenths grams of sodium hydroxide pellets were dissolved in 200 ml. of distilled water and chilled in an ice bath. To this was added, with stirring and continued cooling, a solution of 115 g. of mercaptoacetic acid in m1. of water. With the temperature of the above solution maintained at 75 C., 139 g. of chloropropanol were added from a dropping funnel, with stirring, and when addition was completed, the reaction mixture was stirred and heated for an additional hour. The Water was then removed under reduced pressure until a heavy slurry was obtained. This was extracted with acetone by triturating with 2 one-liter portions, and after pouring off the supernatant acetone, residual acetone was removed under reduced pressure with mild warming. The solid was suspended in 750 ml. of absolute ethyl alcohol and 90 g. of concentrated hydrochloric acid was added with vigorous stirring. The salt was then removed by filtration, washed with 200 ml. of alcohol, and the combined filtrates were concentrated under reduced pressure. The residue was distilled under high vacuum. The portion boiling between 130/2 mm. and 168/ 12 mm. was redistilled to yield the desired product, boiling at 83/0.03 mm./0.05 mm., the major portion at 88/0.05 mm. to 92/0.07 mm. The yield was 15 g., M.P. 42.4 C.

Analysis.-Calculated for C H SO C, 45.5; H, 6.0; S, 24.2 Found: C, 45.7; H, 6.4; S, 24.6.

The polymerization of 'y-hydroxypropylmercaptoacetic acid lactone: In an all-glass outfit equipped with an air condenser were placed 10 g. of 'y-hydroxypropylmercapt0 acetic acid lactone and 0.100 g. of anhydrous zinc chloride. The reaction vessel was placed on a steam bath: with a slow stream of nitrogen bubbling through the melt. At the end of 21 hours on the steam bath, the mixture had. turned quite dark. After cooling to room temperature; under nitrogen, the viscous liquid was dissolved in 20 ml. of acetone, boiled with decolorizing carbon -(Norite), and filtered. An additional 40 ml. of acetone was added and the solution was cooled in an acetone-Dry Ice bath. A. solid deposited. The supernatant acetone was pored off, replaced by 60 ml. of fresh acetone, and the chilling was repeated. Again, the supernatant was poured off, and the residue was dissolved in 30 ml. of acetone at room temperature. This solution was used for test. The solids content was 10.8%.

5 EXAMPLE 8 Polymerized B-hydroxyethylmercaptoacetic acid was obtained by placing a quantity of the acid (monomer) in a stoppered bottle and allowing it to stand for several weeks. The polymer formed spontaneously. It had a molecular weight of approximately .1000.

The novel thiopolymers of our invention can be added to photographic emulsions using any of the well known techniques in emulsion making. For example, the thiopolymers can be dissolved in a suitable solvent and added -to the silver halide emulsion, or can be added to the emulsion in the form of a finely-divided dispersion, such as described in Fierke et al. US. Patent 2,801,171, issued July 30, 1957. The solvent should be so selected that it has no harmful effect upon the emulsion, and generally solvents or diluents which are miscible with water are to be preferred. Water or dilute alkali is a dispersing medium for some of the polymers of our invention. For a preferred embodiment, the polymer can be dissolved in a solvent, such as ethanol, acetone, pyridine, N,N-dimethylformamide, etc., and added to the emulsion in this form.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be eflected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

When we claim as our invention and desire secured by Letters Patent of the United States is:

1. An essentially linear polyester having a molecular weight up to about 10,000 consisting essentially of at least three recurring units represented by the following general formula:

wherein R and R each represents an alkylene radical, said polyester being produced by the condensation polymerization of a compound selected from the group consisting of (1) a hydroxy acid having the formula:

and (2) a lactone having the formula:

wherein R and R are as defined above.

2. A polyester as defined by claim 1 wherein R is a methylene radical and R is an ethylene radical.

3. A polyester as defined by claim 1 wherein R is an ethylene radical and R is a propylene radical.

4. A polyester as defined by claim 1 wherein R is an ethylene radical and R is an ethylene radical.

5. A polymer as defined by claim 1 wherein R is an ethylene radical and R is a hexylene radical.

6. A polyester as defined by claim 1 wherein R is a methylene radical and R is a propylene radical.

References Cited by the Examiner UNITED STATES PATENTS 2,416,052 2/ 1947 Gribbins 260481 2,600,953 6/1952 Aelion 26078 2,917,410 12/1959 Vitalis 26078 JOSEPH SCHOFER, Primary Examiner.

DONALD CZAJA, L. I. BERCOVITZ, Examiners. 

1. AN ESSENTIALLY LINEAR POLYESTER HAVING A MOLECULAR WEIGHT UP TO ABOUT 10,000 CONSISTING ESSENTIALLY OF AT LEAST THREE RECURRING UNITS REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 